001 /* ========================================================================
002 * JCommon : a free general purpose class library for the Java(tm) platform
003 * ========================================================================
004 *
005 * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
006 *
007 * Project Info: http://www.jfree.org/jcommon/index.html
008 *
009 * This library is free software; you can redistribute it and/or modify it
010 * under the terms of the GNU Lesser General Public License as published by
011 * the Free Software Foundation; either version 2.1 of the License, or
012 * (at your option) any later version.
013 *
014 * This library is distributed in the hope that it will be useful, but
015 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
016 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
017 * License for more details.
018 *
019 * You should have received a copy of the GNU Lesser General Public
020 * License along with this library; if not, write to the Free Software
021 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
022 * USA.
023 *
024 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
025 * in the United States and other countries.]
026 *
027 * --------------------
028 * ClassComparator.java
029 * --------------------
030 * (C)opyright 2003, 2004, by Thomas Morgner and Contributors.
031 *
032 * Original Author: Thomas Morgner (taquera@sherito.org);
033 * Contributor(s): David Gilbert (for Object Refinery Limited);
034 *
035 * $Id: ClassComparator.java,v 1.5 2005/11/08 14:22:04 mungady Exp $
036 *
037 * Changes
038 * -------
039 * 02-May-2003 : Initial version
040 */
041 package org.jfree.xml.factory.objects;
042
043 import java.io.Serializable;
044 import java.util.Comparator;
045
046 /**
047 * The class comparator can be used to compare and sort classes and their
048 * superclasses. The comparator is not able to compare classes which have
049 * no relation...
050 *
051 * @author Thomas Morgner
052 * @deprecated Moved to org.jfree.util
053 */
054 public class ClassComparator implements Comparator, Serializable {
055
056 /**
057 * Defaultconstructor.
058 */
059 public ClassComparator() {
060 super();
061 }
062
063 /**
064 * Compares its two arguments for order. Returns a negative integer,
065 * zero, or a positive integer as the first argument is less than, equal
066 * to, or greater than the second.<p>
067 * <P>
068 * Note: throws ClassCastException if the arguments' types prevent them from
069 * being compared by this Comparator.
070 * And IllegalArgumentException if the classes share no relation.
071 *
072 * The implementor must ensure that <tt>sgn(compare(x, y)) ==
073 * -sgn(compare(y, x))</tt> for all <tt>x</tt> and <tt>y</tt>. (This
074 * implies that <tt>compare(x, y)</tt> must throw an exception if and only
075 * if <tt>compare(y, x)</tt> throws an exception.)<p>
076 *
077 * The implementor must also ensure that the relation is transitive:
078 * <tt>((compare(x, y)>0) && (compare(y, z)>0))</tt> implies
079 * <tt>compare(x, z)>0</tt>.<p>
080 *
081 * Finally, the implementer must ensure that <tt>compare(x, y)==0</tt>
082 * implies that <tt>sgn(compare(x, z))==sgn(compare(y, z))</tt> for all
083 * <tt>z</tt>.<p>
084 *
085 * It is generally the case, but <i>not</i> strictly required that
086 * <tt>(compare(x, y)==0) == (x.equals(y))</tt>. Generally speaking,
087 * any comparator that violates this condition should clearly indicate
088 * this fact. The recommended language is "Note: this comparator
089 * imposes orderings that are inconsistent with equals."
090 *
091 * @param o1 the first object to be compared.
092 * @param o2 the second object to be compared.
093 * @return a negative integer, zero, or a positive integer as the
094 * first argument is less than, equal to, or greater than the
095 * second.
096 */
097 public int compare(final Object o1, final Object o2) {
098 final Class c1 = (Class) o1;
099 final Class c2 = (Class) o2;
100 if (c1.equals(o2)) {
101 return 0;
102 }
103 if (c1.isAssignableFrom(c2)) {
104 return -1;
105 }
106 else {
107 if (!c2.isAssignableFrom(c2)) {
108 throw new IllegalArgumentException("The classes share no relation");
109 }
110 return 1;
111 }
112 }
113
114 /**
115 * Checks, whether the given classes are comparable. This method will
116 * return true, if one of the classes is assignable from the other class.
117 *
118 * @param c1 the first class to compare
119 * @param c2 the second class to compare
120 * @return true, if the classes share a direct relation, false otherwise.
121 */
122 public boolean isComparable(final Class c1, final Class c2) {
123 return (c1.isAssignableFrom(c2) || c2.isAssignableFrom(c1));
124 }
125 }